This invention relates to a polishing process, more particularly but not solely to a polishing process suitable for polishing mineral and organic (plastics) opthalmic lenses.
The techniques of glass polishing have been extensively studied in recent years and much more technologically efficient materials are now available than the traditional jewellers' rouge still used twenty years ago. Most of the modern polishing processes are based upon the use of specially developed rare earth compounds or zirconium oxide. Cornish and Watt in "Mechanism of Glass Polishing", Paper at American Ceramic Society Symposium on the Surface Chemistry of Glass, May 9-11, 1966, have given descriptions of the polishing process in general. Silvernail and Silvernail in "The mechanics of glass polishing", Optical World, August 1980, in describing the current theories of the mechanism of the polishing action as the abrasion hypothesis, the flow hypothesis and the chemical-mechanical hypothesis, suggest that the latter has come to be accepted as the principal mechanism. They further define the "polishing activity" in terms of the rate of weight loss of the glass piece during polishing and have been able to make useful predictions of the practical aspects of the behaviour of a polishing powder from an experimental analysis of such data. Gambale and Stone in their U.S. Pat. No. 3,685,218, August 1972, have discussed the beneficial effect of certain additives to the powder and also made clear the necessity to produce a material which will polish glass and do so efficiently; whilst Khaladji in "A quantitative analysis of polishing efficiency obtained on standard machines" S.P.I.E. Vol 109, 1977, has discussed the relationships of powder composition to pad structure, and Transelco in their U.K. Pat. No. 1,398,765, June 1975, have stated "that it is possible to adjust the product (of their invention) to deliver a wide range of desirable properties". The matter of the present invention concerns the relationship of the polishing powder to the water.